Refrigerating system having reverse flow



July 28, 1959 Filed April 22, 1957 2 Sheets-Sheet 1 INVENTOR. FRANK H DUNBB QTTORNEYS United States Patent REFRIGERATIN G HAVING REVERSE Frank H. Dunbar, Miami, Fla., assignor to Frank J. Reilly, Winter Park, Fla.

Application April 22, 1957, Serial No. 654,188

6 Claims. (Cl. 62-282) This invention relates to refrigerating systems and more particularly to such a system having improved means for defrosting the evaporator coils.

In the use of refrigerating systems, it is well known that the evaporator coils to which the refrigerant is delivered for the cooling effect become frosted on the outer surfaces of the coils. The accumulation of such frost on the coil surfaces reduces the efficiency of the refrigerating system and so it is common practice to defrost the evaporator coils from time to time. Usually, the defrosting of the coils is effected by shutting down the refrigerating system for a period of time suflicient to enable the accumulated frost to melt on the coils. However, this expedient is inconvenient in many instances, as it limits the operating periods of the system.

The present invention has for its principal object the provision of a refrigerating system in which the evaporator coils can be easily defrosted or maintained in a non-frosted condition without the necessity of shutting down the refrigerator system.

A refrigerator system made according to the invention, comprises two sets of spaced evaporator coils, an air blower having an air inlet and an air outlet, and air ducts communicating separately with the chamber to be cooled through the spaces between the coils of the respective sets of evaporator coils. In other 'words, each duct is adapted to feed air to or receive air from the chamber to be cooled by way of one of the two sets of evaporator coils. The system also comprises damper means having a first position for connecting. one of these ducts to the blower inlet and the other duct to the blower outlet and thereby effecting circulation of air from the blower through one of the coil sets, the chamber to be cooled, the other coil set and back to the blower. The damper means are movable to a second position to connect the afore-mentioned one duct to the blower outlet and the afore-mentioned other duct to the blower inlet and thereby reverse the direction of the air circulation by the blower. Mechanism is provided for shifting the damper means back and forth from one position to the other so as to effect circulation of the air first in one direction and then in the other direction by the blower. Thus, the direction of air circulation is reversed intermittently without reversing the direction of rotation of the blower.

With this arrangement, any frost accumulating on the evaporator coils of one set during circulation of the air in one direction is melted and thus removed from these coils when the direction of air circulation is reversed by operation of the damper means; and any frost accumulating on the other set of coils as a result of this reversal of the circulating direction is melted and thereby removed from the coils when the direction of circulation is again reversed by operation of the damper means. Accordingly, the refrigerating system can be operated continuously without accumulating sufficient frost on the evaporator coils to impair the efficiency of the system materially. In fact, by operating the damper means to effect the reversals of the circulatinlg direction frequently, 'which may be done automatically, the evaporator coils can be maintained free of any substantial accumulation of frost.

In the preferred form of the new system, the damper means include two dampers operatively connected to the shifting mechanism. These two dampers are operable to close openings in the respective ducts, which openings communicate with either the inlet or the outlet of the blower; and the two dampers are also operable to move alternately into alignment with a dividing edge common to the two ducts and located opposite the other of the blower inlet and outlet. For example, the dividing edge common to the two ducts may be located opposite the blower outlet, and the openings in the respective ducts may be connected to the blower inlet. Thus, in one position of the dampers, one of the ducts is shut off from the blower outlet by one of the dampers, but communicates with the blower inlet by way of the corresponding duct while the other duct is in communciation with the blower outlet but has its corresponding opening shut off from the blower inlet by the other damper; and in the opposite position of the dampers these connections are reversed. Also, I prefer to provide air splitters located adjacent the blower outlet so as to divide the stream of air passing to one or the other of the two sets of evaporator coils, depending upon the position of the damper means. In this way, the .air flow is distributed substantially uniformly through the spaces between the coils as the air flows to the chamber to be cooled. The air splitters are preferably located between the two dampers and are operatively connected thereto so as to direct the air first to one of the coil sets and then to the other coil set as the dampers are shifted back and forth.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which Fig. 1 is a schematic view of a preferred form of the new system and Fig. 2 is an enlarged vertical sectional view of the system illustrated in Fig. l. 7

Referring to the drawings, I have there illustrated a refrigerating system which is particularly adapted for use in cooling perishable products in a shipping vehicle, such as a freight car or a truck, so that the products will arrive at their destination in marketable condition. However, it is to be understood that the invention is not limited to this particular use.

The chamber to be cooled (such as the interior of the freight car or truck previously mentioned) is indicated in Fig. 1 at 10. The refrigerating system, as shown, comprises housings 11 and 12 for two sets of evaporator coils. As shown in Fig. 2, the housings 11 and 12 contain evaporator coils 11a and 12a, respectively.

It will be understood that these two sets of coils 11a and 12a are connected into a conventional refrigerating circuit including the usual compressor and expansion val-ye (not shown) so that the surfaces of the coils are ngtmtained at low temperature to provide a cooling e ect.

The system also comprises a blower 13 having an air-outlet 13a at the periphery of the blower housing and an air inlet 13b at the central portion of the housing. The blower 13 may be of the centrifugal type provided with a blade rotor (Fig. 2), the air being discharged through the blower outlet 13a tangentially of the rotor, and incoming air being delivered to the eye of the rotor, through the central inlet 13b, as will be readily understood by those skilled in the blower art.

Between the blower 13 and the housings 11 and 12 for the two sets of expansion coils are two ducts 14 and 15, these ducts converging from the coil housings and toward. the blower. These ducts are adapted to be connected to the blower inlet and outlet, respectively, by damper means comprising two dampers 16 and 17.v The dampers 16 and 17 are arranged in parallel spaced relation and have corresponding ends pivoted to the: blower housing 13 as shown at 16a and 17a, respectively, these pivots being located at opposite sides of the blower outlet 13a. Directly opposite the outlet 13a, the ducts 14 and 15 form a common dividing edge 18 with which the dampers 16 and 17 are adapted to align or engage alternately. These dampers are also adapted to cover lateral openings 19 and 21 in the respective ducts 14 and 15. These openings 19 and 20 communicate with the blower inlet 1317 by Way of inlet ducts: 21 and 22, respectively (Fig. 1).

The dampers 16 and 17 are interconnected by a link 24 which holds them in parallel spaced relation. shift the dampers back and forth about their respective pivots 16a17a I provide a shifting mechanism com prising a linkage 2525a connecting the damper 16 toa shaft 26 rotatably mounted in any suitable manner on a fixed part of the system. The shaft 26 is adapted to be rocked back and forth by an actuating arm 26a- The latter may be operated manually or it may be operated mechanically by means of a motor-actuated cam (not shown) engageable with a follower 26b on the actuating arm 26a. It will be understood that movement of the actuating arm 26a back and forth between its full line and broken line positions (Fig. 2) will cause the dampers 16 and 17 to move back and forth between the produce in chamber 10. At the same time, the flow of air in this new direction serves to remove or prevent any frost formation on the evaporator coils which are most susceptible to frosting during the previous circulation in the first direction. After a period of circulation in this new direction, the arm 26a is again actuated to return the parts to their initial positions so that the direction of circulation of the air by the blower 13 is their full line and broken line positions through the linkage 25-4511.

The rotor 130 of the blower is driven by a motor 28 through a driving belt 29.

In the use of the refrigerating system, the housings 11 and 12 for the evaporator coils are connected through adaptors 11b and 12b, respectively, to the interior of the chamber or compartment 10, to be cooled. As illustrated, the coil housing 11 communicates through its adaptor with the upper part of the chamber 10, and the coil housing 12 communicates through its adaptor with the lower part of the chamber.

Assume that the dampers 16 and 17 are in the positions shown in Fig. 1, wherein the free end of damper- 1 6 is aligned with the common dividing edge 18 and the damper 17 closes the opening 20 in duct 15. The blower 13 will then circulate air from the blower out- .let 13a through the space between the dampers, duct 15, the housing 12 for the second set of evaporator coils, adaptor 12b, the interior of chamber 10, adaptor 11b, coil housing 11, duct 14, the corresponding opening 19, and back to the blower by way of duct 21 and inlet 1312. Thus, the contents of the chamber 10 will be cooled by the cool air entering this chamber after passing through the spaces between the coils 12a, and the air will be circulated by the blower through'the path previously described. While the air is so circulating, the actuating arm 26a of the shifting mechanism is in the broken line position shown in Fig. 2.

When the'actuating arm 26a is shifted to the full.

line position shown in Fig. 2, the dampers are lifted to their opposite positions wherein the damper 17 is now in alignment or contact with the common dividing edge 18, and the damper 16 closes the opening 19 of duct 14, the opening 20 of the other duct being uncovered. Consequently, the blower 13 now circulates air from outlet 13a between the dampers, through duct 14, coil housing 11, adaptor 11b, the interior of chamber 10,

adaptor 12b, coil housing 12, duct 15, the correspond-' ing opening 20, and then back to the blower inlet 13b by way of duct 22. In other words, the direction of circulation of the cooling air has now been reversed."

This air circulation in the new direction proceeds so as to continue the refrigerating action and the cooling of again reversed, the flow then being in the direction first described. The refrigerating action then continues, and at the same time the circulation of air in the initial direction serves to defrost or prevent .frosting of the evaporator coils which are most susceptible to frosting during circulation of the air through the second path previously described, that is, after the first reversal of the circulating direction.

It will be understood that the operation of the system proceeds in the manner previously described, with an intermittent shifting of the dampers 16 and 17 back and forth to effect reversal of the direction of flow of the cooling air from time to time.

Adjacent the blower outlet 13a is a series of air splitters 31 located between the dampers 16 and 17. The splitting elements 31, as shown, are in the form of flexible metal sheets extending across the outlet 13a in parallel spaced relation and secured at corresponding ends of the blower housing located above and below the outlet 13a, as indicated at 32. The air splitters 31 extend from their fixed ends away from the blower outlet and into the space formed by the junction of the ducts 1d and 15, and at their free ends the splitters 31 are interconnected by a bar 33. The bar 33, in turn, is connected at one end through a link 34 with the damper 17. Accordingly, as the dampers 16 and 17 are moved back and forth, the air splitters 31 are moved back and forth about their fixed ends so that the splitters are maintained in substantial parallelism with the dampers at all times. With this arrangement, the splitters 31 serve to sub-divide the air stream issuing from the blower outlet 13a so that the stream is more evenly distributed through the spaces between the coils 11a or 12a (depending upon the positions of the dampers), as the air flows to the chamber 10 to be cooled.

The reversal of the cold air flow not only provides a defrosting action but also results in better cooling of the contents of chamber 11). That is, each reversal causes the cold air to strike the crated citrus fruit or other produce which has 'been in contact with the warmer air leaving the chamber 10. Thus, it causes the coldest air to strike the warmest fruit and thereby obtain the greatest heat exchange and fastest cooling. Also, the

reversal of the air causes it to find new channels through the pack in chamber 10 and to strike the portions of crates and of individual fruits which have been in the I lee of the former current. Not only does this constant picking up of heat cool the load much faster, but the air is warmer when it returns to the conditioner and this also prevents frosting of the coils.

I claim:

1. In a refrigerating system for cooling an enclosed said edge and wherein the dampers connect one of the ducts to the blower inlet and the other duct to the blower outlet, said dampers having a second position in which the other damper is in alignment with said edge,

and wherein the dampers connect said one duct to the blower outlet andsaid other duct to the blower inlet,

thereby reversing the direction of air flow through the coil sets and the chamber, and shifting mechanism operatively connected to the dampers (for shifting them from one position to the other and thereby moving the dampers alternately into alignment with said dividing edge.

2. A device according to claim 1, in which the dividing edge is located opposite one of said inlet and outlet, each duct having an opening communicating with the other of said inlet and outlet, one of the dampers being in alignment with said edge while the second damper closes one of the duct openings in said one position of the dampers, the second damper being in alignment with said edge while the first damper closes the other duct opening in said second position of the dampers.

3. A device according to claim 1, comprising also splitter elements adjacent the blower outlet for dividing the air stream passing through said outlet.

4. A device according to claim 3, in which the splitter elements are disposed in substantially parallel spaced relation and are connected to the dampers for movement therewith.

5. A device according to claim 3, in which the splitter elements are disposed in substantially parallel spaced relation and are fixed at corresponding ends, the opposite ends of the splitter elements being connected to the dampers for movement therewith.

6. A device according to claim 1, comprising also splitter elements adjacent the blower outlet for dividing the air stream passing through said outlet, the splitter elements being located between the dampers and connected to the dampers for movement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,763,132 Jue Sept. 18, 1956 

